In order to limit exposure of humans to toxic and/or hazardous chemicals, protective clothing materials have been developed which provide protection against exposure to these chemicals. Personnel required to wear garment systems fabricated from protective clothing materials include those workers at chemical manufacturing sites who risk coming in contact with toxic and/or hazardous chemicals in spite of engineering controls implemented to contain these chemicals. Personnel are also required to wear garment systems for protection against exposure from toxic and hazardous chemicals where engineering controls are not available to minimize their exposure to the hazardous chemical agents, such as for example during remediation of a hazardous waste site, or in an emergency situation such as a chemical spill or fire or during chemical warfare where military personnel may be exposed to such noxious chemical agents as blister agents such as Mustard gas or nerve agents during military operations.
Contact with these toxic and/or hazardous chemicals can result in harm to the human body ranging from acute trauma, such as dermatitis, burns or poisoning, to chronic effects such as cancer.
Toxic and/or hazardous chemicals may affect protective clothing materials in various ways. The toxic and/or hazardous chemical may degrade protective clothing materials by effecting a deleterious change in one or more physical properties of the protective clothing material upon contact with the toxic and/or hazardous chemical. The toxic and/or hazardous chemical may penetrate protective clothing materials through closures, pores or other imperfections in the protective clothing material. The toxic and/or hazardous chemical may permeate protective clothing materials through the chemically protective material on a molecular level. When the toxic and/or hazardous chemicals present a risk in minute quantities, chemically protective materials must limit the permeation of the chemical through the material for a period of time.
Permeation rates of a particular toxic and/or hazardous chemical for a given chemically protective material are ordinarily determined on a per unit thickness basis. To predict the degree of protection offered by a particular chemically protective material against a particular chemical challenge, one must have a chemically protective material with a predictable thickness. Increasing thickness of a chemically protective material may not be desirable in a certain chemically protective material since too great an increase in thickness of the chemically protective material may decrease that chemically protective material's aesthetics and drape. Increasing the thickness of a chemically protective material may also result in an increase in the weight per unit area of the chemically protective material thereby decreasing the aesthetics of articles produced from the chemically protective material.
Typically, chemically protective materials have been fabricated from polymeric materials, such as butyl rubber, nitrile rubber, and fluorinated rubbers such as for example Viton.RTM. rubber. These materials may be used alone to fabricate chemically protective materials or in combination with reinforcing materials such as polyamide or polyester fabric to provide additional strength to the chemically protective materials.
Fluoropolymers have also been used as a barrier to chemical exposure. Fluoropolymers are of great utility due to their chemical inertness. These materials are also combined with reinforcing materials so that extra strength is provided. However, fluoropolymers typically have poor aesthetics and do not provide adequate drape for garments.
One type of fluoropolymer barrier material is taught in U.S. Pat. No. 4,610,918 to Effenberger et al. This patent teaches a wear-resistant fluoropolymer-containing flexible composite. The composite is produced through a process of initially coating a flexible substrate such as glass fabric or a metal mesh with a dispersion of a fluoropolymer such as polytetrafluoroethylene and subsequently coating the flexible substrate with a blend of a fluoropolymer, such as polytetrafluoroethylene and a "hard polymer". The resultant fluoropolymer barrier material is said to resist cracking. However, obtaining a consistent coating thickness without any thin areas or pin holes would be quite difficult using the above-mentioned process of dispersion deposition.
Another type of fluoropolymer barrier material is taught in U.S. Pat. No. 4,816,330 to Freund et al. This patent teaches a chemically resistant garment material formed from a laminate of skived polytetrafluoroethylene adhered to a cloth substrate. Skived polytetrafluoroethylene is said to be virtually pin hole free and therefore provides an improvement over polytetrafluoroethylene dispersion coated fabrics in permeation resistance.
Another type of fluoropolymer barrier material is taught in U.S. Pat. No. 4,946,736 to Sassa. This patent teaches a laminate composed of various layers which is useful as a covering for a radome as well as being useful as a material in protective garments. This laminate is produced by first laminating a woven polytetrafluoroethylene fabric impregnated with an amount of a polytetrafluoroethylene dispersion to a porous polytetrafluoroethylene layer. A second laminate is produced by adhering a second porous polytetrafluoroethylene layer to a thermoplastic polymeric layer such as fluorinated ethylene propylene (FEP). Subsequently, the thermoplastic polymeric layer of the second laminate is adhered to the porous polytetrafluoroethylene layer of the first laminate to form the fluoropolymer barrier material. While this laminated material appears to exhibit acceptable aesthetic qualities for use as a chemically protective barrier material, the thermoplastic polymeric layer exhibits inconsistent thicknesses resulting from deformation of the thermoplastic polymeric layer against the polytetrafluoroethylene fabric in the final lamination step. These inconsistent thicknesses have a detrimental effect on the permeation resistance of this material thereby limiting its utility in protective garments.